question on frontline

Hello,

I treat my dog, Jasper, with frontline plus each month. Today I bathed him, and afterwards found a tick buried behind his head. I was able to get it out and it was dead. I thought the frontline was supposed to keep them from biting? Perhaps it is not working as well as I had hoped? Any thoughts?

Also, how long should I wait before I expect to see dead fleas after frontline treatment? I found a couple on my cat and treated him today, but tonight I still am pulling out quite alive fleas. I know it says 18 hours, but I thought it would kill at least some of them by now. Perhaps I am being too hasty?

Thanks, Kim